Percussive hand tool



Jan. 23, 1934.

J. J. RAWL-INGS PERCUSSIVE HAND TOOL Filed Feb. 11, 1933 k IIIIIIIIIA Aka-m Patented Jan. 23, 1934 UNETED STATES was ears

1,944,572 rsaocssrvn HAND roof.

Application February 11,1933, Serial No. 656,319, and in Great Britain February 27, .1932

ZClaims. (o1.255-41) This invention relates to an improved percussive hand tool chiefly intended for use in boring or drilling holes in masonry, brickwork and the like, and applicable to other operations, for example, such as riveting or staple driving, for which a hammer can be or is usually employed.

According to this invention, in a hand tool of the kind operated by means of a crank handle to which rotary motion is imparted by the hand of the user to rotate a shaft which actuates a hammer member by means of a cam acting to move the hammer member in one direction, movement of this member in the opposite direction being efiected by a spring, the said spring acts through a lever oscillated by the cam. Means are also provided whereby in the rotation of the shaft carrying the cam above mentioned, an intermittent rotary movement is imparted to the drill shank or like part receiving the blows delivered by the hammer member.

In the accompanying drawing:

Fig. 1 shows a side view of a percussive hand tool in accordance with this invention, with a part of the casing removed.

Fig. 2 shows a section on the line 2-2, Fig. 1.

Fig. 3 shows a section on the line 3-3, Fig. 1.

Fig. 4 is a detail view of one end of the drill shank and associated parts, drawn to a larger scale.

Figs. 5 and 6 are, respectively, side and end detail views of means for rotating the drill shank.

Fig. 7 is a sectional view of a modified form of the shank rotating cam.

Fig. 8 is a view of a modified arrangement hereinafter described.

As shown in Fig. 1, a is a casing preferably comprising two symmetrical parts of which one part has been removed to expose the mechanism mounted in this casing. A part of extension of the casing is shaped to serve as a handle b. A cam spindle a mounted transversely in the casing extends out from opposite sides of the casing, providing screw threaded parts to receive a crank handle (1 which can be transferred to opposite sides of the casing as required to be rotated by the right hand or the left hand of the user. The spindle 0 can be driven in any other convenient manner, for example, by a small electric motor or a flexible driving shaft. On the spindle 0 near to opposite sides of the casing, cams e are mounted to act each upon a corresponding lever pivotally mounted on a cross bar 9. The lever f is pressed into contact with the cam e by a spring h in compression between a plate 2' supported by trunnions k: respectively mounted in the levers j on opposite sides thereof, Fig. 2, and a plate l pivotally carried by a screw m engaged in a nut n fixed in the casing 17. and thus providing a means for adjusting the compression of the spring h. A The levers f are pivotally connected by pins 0 to a 60 hammer 1) provided with a tail rod q guided in a lug r through which it moves with a sufficient freedom to allow the angular position of the hammer axis to change as the hammer is moved by oscillations of the levers f. a

With this construction, as the spindle c is rotated. the cams c move the levers and hammer p from the position shown in full lines in Fig. 1 to the positions shown in broken lines until the high parts of the cam move out of contact with the noses s of the levers, whereupon the spring It moves the levers so as to throw the hammer suddenly against the head t on the shank u of a drill holder 1), continuous rotation of the spindle thus causing the hammer to strike a succession of blows,

In order to effect small movements of the drill holder 22 about its longitudinal axis intermittently between each blow of the hammer, the head t is Y made rectangular or with flattened sides, Fig. 3,30 and extends'through a hole w, Fig. 4, of a corresponding shape in a toothed wheel as mounted to rotate in the casing a coaxially with the drill holder shank and held against axial movement. The head 1? is loose in the hole w and the shank u is loose in a sleeve y, so that the drill holder can move freely under the blows of the hammer.

A space 2 serving as a receptacle for lubricant can be formed within the sleeve ,1; to supply lubricant to the shank u and the wheel a.

An intermittent rotation of the shank u is effected by means of a cam 1 on the spindle 0 engaging the teeth of the wheel 9:. The cam 1 can be conveniently constructed with helical ribs 2 M each extending for a convenient angular distance,- for example 90, around the cam axis and each commencing at the same axial-plane as that at which the preceding rib terminates, the axial displacement between the ends of each rib being equal to the pitch of the teeth of the wheel .r. This cam can be made from a casting or built up from pressed plates. Any other convenient construction of cam can be substituted for that hereinabove described. A suitable cam can be built up of plates 3 (Fig. 7) clamped between side plates l'05 l, each plate 3 being of a substantially quadrantal shape and having a part thereof projecting beyond the circumference of the plates 4 bent to the required helical contour. U

In order to render rotation of the spindle c in-'l10 operative to effect the percussive movements of the hammer p as shown in Fig. 1, a screw 5 engaged in a nut 6 fixed in the casing can be protruded into engagement with the plate 2 and, the compression of the spring 71. being relieved by retracting the screw m, the levers 7 can be moved to a position in which the noses s of the levers are out of the path of the cam e. Rotation of the spindle 0 will then be efiective only to rotate the drill holder 11, the improved hand tool then serving as a brace for boring holes by means of a rotary drill or bit. Owing to the speed reduction from the spindle c to the wheel 11:, this tool is especially suitable for use for drilling brick, marble, glass and like material.

An alternative construction allowed the hand toolto be used as a brace and avoiding theuse of the screw 5, is shown in Fig. 8; In this construction the spring h is arranged between a ring '7 mounted in the levers ,f, and a nut 8 on the screw m. A stirrup 9 attached to the nut 8 and passing round a bar in the ring 7 limits the separation of the nut and stirrup. The screw m has a shouldered portion mounted in a-bearing 10 in the casing so that it can rotate without axial movement. Rotation of the screw to move the nut 8 in one direction'then compresses the spring h whilst movement of the nut in the opposite direction first relieves the loading of the spring and then by the stirrup 9 moves the levers 1 out of track of the cams.

I claim:

1. A percussive hand tool comprising a casing, a

lever pivotally mounted in said casing, a hammer pivoted to the end of said lever, a cam wheel mounted for rotation in said casing and adapted to engage said lever, a spring acting upon the other .end of said lever for bringing it back to its normal position after engagement by said cam wheel and for imparting the required impulsion to the hammer, means for adjusting the stress of said spring, a rotatable tool holder supported and guided in the casing so as to receive the blows of the hammer, a toothed Wheel mounted to rotate in the casing coaxially with the tool holder, means for preventing axial movement of said toothed wheel which has a hole engaged by said tool holder, the arrangement being such that the tool holder can freely move axially and rotate by the turning movement of the toothed wheel, a second cam wheel having helical ribs engaging the teethof said toothed wheel, and means for simultaneously driving both cam wheels, substantially for the purpose set forth. 7

2. In a percussive hand tool comprising a casing, a lever pivotally mounted in said casing, a hammer pivoted to the end of said lever, a cam wheel mounted for rotation in said casing and adapted to engage said lever, a stirrup connecting the other end of said lever to a nut'capable of moving along a rotatable screw fitted in the casing and prevented against axial movement, and a helical spring surrounding said stirrup and held between said second lever end and the nut, for the purpose set forth.

JOHN JOSEPH RAWLI GS. 

